In an existing long term evolution (LTE) system, a subframe is a smallest time unit scheduled by a base station (eNB, Evolved NodeB), each subframe includes two timeslots, and each timeslot includes seven symbols. For a scheduled UE, a subframe includes a physical downlink control channel (PDCCH, Physical Downlink Control Channel) of the user equipment (UE, User Equipment), where the PDCCH is borne in first n symbols of the subframe, and n may be any one of 1, 2, and 3, or any one of 2, 3, and 4 (in a case where the system bandwidth is 1.4 MHz).
The PDCCH carries a downlink scheduling grant (DL_grant, Downlink_grant) or an uplink scheduling grant (UL_grant, Uplink_grant), which respectively carries scheduling information of a physical downlink shared channel (PDSCH) or a physical uplink shared channel (PUSCH). Depending on different specific data types (for example, multiple input multiple output (MIMO) and non-MIMO data), the PDCCH may have different downlink control information (DCI, Downlink Control Information) formats. For example, the DCI formats may be 0, 1, 1A, 2, 2A, 2B, and 2C. A payload size (referred to as a payload size in a standard text) of the PDCCH corresponding to these DCI formats generally varies.
In the existing LTE system, PDCCH demodulation is uniformly based on a cell-specific reference signal (CRS, Cell-specific Reference Signal). FIG. 1 is a schematic diagram showing that a PDSCH is scheduled by a PDCCH in a subframe in the prior art. In FIG. 1, a horizontal axis represents a time domain, and a vertical axis represents a frequency domain. In the prior art, PDCCH information does not undergo MIMO precoding processing, and the UE may obtain information of an antenna port for transmitting PDCCH by detecting a broadcast channel. Specifically, after the UE demodulates and decodes a PDCCH in time-frequency resources of a search space of the PDCCH according to the payload size of the PDCCH and an aggregation level of a control channel element (CCE), the UE uses a UE-specific radio network temporary identifier (RNTI) to perform descrambling CRC to check and determine the PDCCH of the UE, and performs, according to scheduling information in the PDCCH, corresponding reception and transmission processing for a PDSCH or PUSCH scheduled by the PDCCH.
In an LTE system of a later release, technologies such as carrier aggregation, multi-user multiple input multiple output (MIMO, Multiple Input Multiple Output), and coordinated multiple points (COMP, Coordinated Multiple Points) will be introduced. In addition, a heterogeneous network scenario will be widely applied. All these will lead to a capacity limitation on the PDCCH. Therefore, a PDCCH based on channel information precoding will be introduced. This PDCCH will be demodulated based on a UE-specific reference signal. In this case, the UE-specific reference signal may be referred to as a dedicated reference signal (DRS, Dedicated Reference Signal), while the PDCCH demodulated based on the DRS is briefed as a D-PDCCH. Through the D-PDCCH, a precoding gain may be obtained to improve performance.
FIG. 2 is a schematic diagram showing that a PDSCH is scheduled by a D-PDCCH in a subframe in the prior art. D-PDCCH resources are located in a PDSCH region, and the D-PDCCH and the PDSCH scheduled by the D-PDCCH are divided by frequencies.
However, in the prior art, the UE can only detect the PDCCH based on a non-precoding manner and according to the CRS. For the D-PDCCH based on MIMO precoding, the prior art does not provide a detection method. If the D-PDCCH cannot be detected, data transmission is definitely impossible. Therefore, how to ensure that the UE detects the D-PDCCH is a pressing issue to be solved.